Enlarging the diameter of hollow metal articles



Dec. 14, 1937.

F. SINGER 2,102,099

ENLARGING THE DIAMETER OF HOLLOW METAL ARTICLES I VII/1 W/TNEJJES Filed Jan. 28, 1956 2 Sheets-Sheet 1 INVENTOR 2 ATTORNEYZ F. SINGER 2,102,099

ENLARGING THE DIAMETER OF HOLLOW METAL ARTICLES Dec. 14, 1937.

2 Shets-Sheet 2 Filed Jan. 28, 1936 INVENTOR.

BY I 2 QM, @A aw 605 ATTORNEYS.

Pat enter] Dec. 14, 1937 UNITED STAT nmnamo rnn DIAMETER or nomow METALAB'I'ICLES Fritz Singer, Nuremberg, Germany, assign'or to v Tllblll A. G Gllflll, Swltaerland Application January '28, 1936, Serial No. 61,152 In Germany May 14, 1934 4 Claims.. (01. 205-4) This invention relates to the enlarging. of-the diameter of hollow metal articles while avoiding more than a moderate reduction of the wall thickness.

It is among the objects of the invention .to provide a method of enlarging the diameter, i. e. ex-

panding, of hollow metallic articles, such as tubes, which efi'ectively expands the tubes without great change in wall thickness, is simple, eflective and readily practiced. and whose practice requires only simple, compact and relatively inexpensive apparatus.

A further object is to provide apparatus for performing the method. I

The invention willbe described with reference .to the accompanying drawings in which Fig. 1 -is a longitudinal sectional view through the preferred embodiment of apparatus adapted for the [practice of the method; and Fig. 2 a plan view,

1tg lartljy in section, of the apparatus shown in- Figure 3 is a longitudinal sectional view, partly broken away, diagrammatically showing a smoothing die over the emerging, extremity of the enlarged tube.

In accordance with the invention thearticle, such as a tube, is expanded by advancing a relatively short length over a tapered mandrel whose diameter is greater than that of the tube and is productive of the desired enlarged diameter. Successive portions of the tube are then advanced stepwise over the mandrel. The portions advanced over the mandrel expand freely, i. e., they do not move between the mandrel and a die to cause reduction of wall thickness but rather are Suitably the tube is mounted on a mandrel rodv the rear end of which is removably mounted in the machine frame and the free front end of which is provided with a tapered expanding mandrel head the diameter of which is greater than the inner diameter of the tube to be enlarged.

The advancing of the tubular article is efiected by means of any suitable feeding or tube-gripping mechanism mounted on a machine part for reciprocation in the direction of the axis of the.

supporting, or mandrel. rod. Reciprocation of any suitable means, for instance a crank. The gripping mechanism may be of any automatic kind or controlled by suitable means in such a manner that atthe beginning of the forward stroke of the gripping mechanism carrier the tubular article isgripped while it is released when said carrier returns to its initial position. In this manner the tube is gripped and moved forwardly to advance a relatively-short length over the mandrel head. The gripping mechanism then releases the tube and is retracted; it then grips the tube and is again advanced to move another por-' tion of the tube onto the mandrel head.

Thus the method provided by the present invention differs from certain known processes in that the mandrel is not reciprocated but is mount? ed fast, and in that the tube expands freely. The enlarging of the tube is effected exclusively by periodically advancing the tube on its axially fixed supporting rod towards the fixed mandrel head.

Accordingly in the present method only the gripthe gripping mechanism carrier is performed by ping mechanism carrier has to be reciprocated, thus effecting simultaneously feeding of the tube and enlarging of its diameter. A further'feature of the present invention which constitutes an advance over'older methods consists in that tubes of great lengths and small wall thicknesses can be worked"in the hot or cold states while with the prior-processes only hot thick-walled tubes of small lengths could besuccessfully treated due to the bending strains exerted on the mandrel. For

, enlarging thick-walled short tubular articles there is in practice no need as such tubes can be produced directly by known rolling and pressing processes in a. more economical manner and in great lengths.

As the apparatus necessary for performing the process according to the invention is of very simple construction and requires only very small investment cost, the invention may advantageously be used for extending the range of tube sizes tobe produced by means of existing tubeproducing equipment. Furthermore it can be utilized for smoothing the inner surface of roughly rolled or pressed tubes, and it is adapted for completely or partially enlarging tubular articles. I

By my new process I can, for instance, satisfactorily convert brass or steel tube having an outer' diameter of 0.945 inch into a tube having an outer diameter of 1.1 inch with a reduction of wall thickness of only about 8 per cent.

Although the tube expands freely on the mandrel head, it may .in some instances be advantageous to use a die ring, not for the purpose of obtaining any substantial reduction of the wall thickness but in order to smooth the outer surface of the tube whereby tubes can be produced of absolutely smooth and cold-hardened inner and outer surfaces. Such a ring as used in the practice of this invention is shown at K in Fig ure 3 and does not effect any great reduction in wall thickness.

Although various forms of apparatus may be used for practicing the method as thus described, I now prefer to use an apparatus designed purely for enlarging because it can be of simple and inexpensive design. Having reference to the accompanying drawings, which show the preferred embodiment, a tube I is slidably supported on a mandrel rod 2 which is provided at its forward end with a cylindrical mandrel head 3 having a diameter greater than the inside diameter of the tube and adapted to produce a desired increase in tube diameter. A tapered, or conical, portion A connects the cylindrical surface 5 of the mandrel head and the cylindrical surface of the rod. At its rear end rod 2 is removably supported by a rod carrier 6 mounted on a rearwardly extending arm I of the machine frame 8 by means of screws 9, arm i being secured to the machine frame by means of screws II).

To permit the end of supporting rod I to be cleared in order to receive a tube I it is provided with a reduced portion II which engages recesses i2 and i3 in the upper end of rod carrier 6 and a cover-plate M which by means of screws i5 is secured to rod carrier 6.

A crank shaft i6 is journaled in the side walls of machine frame 8. The crank pin I'll of the crank shaft is connected to one end of a push rod It the other end of which is journaled in a slide block [9 slidably disposed in a slot 29 provided in a downwardly extending arm 2i of a carrier 22 for the feeding mechanism. Secured to the slide block i9 is a stud 23 which coaots together with the downwardly bent arm 24a of a fiat-faced lever 24 journaled on a pin 26 carried by lugs 25 of the front part of the feeding mechanism carrier arm 2|. The upwardly extending arm 24b of lever 24 is bifurcated to provide for free passage of the tube and the supporting rod therethrough. The bifurcated ends of the upwardly extending arm 24b of lever 24 form an abutment for a coil spring 21 encircling the tube between said arm 24b and the clamping jaws 28 of the feeding mechanism.

The feeding mechanism is mounted between side walls 29 on the feeding mechanism carrier 2| and consists of the outer supporting blocks 39 secured by screws 3! to the side walls 29, wedge pieces 32, rollers 33, the clamping jaws 28 and the chuck 34. Springs 35 constantly urge the rollers to the left, thus releasing the clamping jaws and the chuck. The side walls 29, 29 are prevented from spreading by any convenient means not shown, such, for example, as forming the two side walls in a single piece or encircling them with a hood or bonnet comprising a cover plate 36 and integral downwardly depending flanges.

The operation of the apparatus is as follows: In the position of the crank as shown in Fig. 1 slide block I9, and consequently stud 23, are in their right-end position. As there is no pressure on the spring coil 21, the chuck 34 is released through the action of springs 35 on rollers 33, thus permitting free passage of the tube while the latter is slipped on supporting rod 2 so as to engage the tapered end of the mandrel 5. After securing the rear end of the supporting. rod 2 on the rod carrier 6, the crank drive is set into motion. During the first part of the crank stroke the slide block i9 and the stud 23 are advanced to the left. when the stud 23 contacts arm 24a. of the lever 24 the latter is caused to move in a clockwise direction so as to compress spring 21 thereby forcing the clamping jaws 28 to move to the right causing rotation of the rollers 33 and thereby the clamping jaws 28 are pressed towards the chuck 34 thus gripping the tube.

As soon as the front face of slide block l9 contacts arm 2| the feeding mechanism carrier 22 together with the lever 24 are moved to the left thereby advancing tube l on the supporting rod 2 towards the mandrel 5 and enlarging a relatively short portion of the tube. During the first part of the,return stroke of the crank only the slide block 19 is returned within the recess 20, which results in the stud 23 releasing arm 24a of lever 24, the pressure on spring coil 2'7 is released, and the tube is likewise released by the jaws. As soon as the back face of slide block l9 contacts arm 2|, the feeding mechanism carrier is returned to its initial position. The tube being released from the frictional grip of the chuck the feeding mechanism is allowed to slide over the tube held fast by the frictional grip of the tube on the mandrel 5. On the next rotation of the crank the cycle is repeated, thus enlarging the diameter of the next succeeding portion of the tube, and this is repeated until the tube, or a desired portion, has been enlarged.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention, and have illustrated and described what I now consider to be its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. That method of expanding hollow metallic articles, such as tubes, which comprises gripping and advancing a relatively short length of the article freely over a tapered mandrel head having a diameter greater than that of the article, and repeating such advancement step-by-step to expand continuously successive relatively short lengths, and thereby freely expanding the diameter of the article with relatively low change in wall thickness, the said gripping taking place a relatively short distance from the mandrel head.

2. That method of expanding hollow metallic articles, such as tubes, which comprises mounting the article on a mandrel removably mounted at its rear end and provided at its forward end with a tapered expanding head having a diameter greater than that of the article, gripping the article and forcing a relatively short length over said head to freely expand said length thereover, and repeating such advancement step-by-step to expand continuously successive relatively short lengths, and thereby freely expanding the diameter of the article with relatively low change in wall thickness, the said gripping taking place a relatively short distance from the mandrel head.

3. Apparatus for enlarging the diameter of tubular metallic articles comprising a frame, a mandrel rod having its rear end removably mounted in said frame and provided at its forward end with atapered expanding head, said expanding head being free of encircling tubecompressing means, and means for successively advancing relatively short lengths of a tube along said mandrel rod and over said head to freely expand the tube with relatively low changes in movement axially and laterally of said rod, a

[block rigidly mounted in said carrier adjacent each of said Jaws. means operated by said reciprocating means during the first part of its forward w stroke for moving said jaws rearwardly of said blocks, means associated with each block for moving the adjacent jaw iateralLv into gripping engagement with said tube when said jaw is moved rearwardly 01 said block, and means for moving said jaws forwardly of said blocks whensaid reciprocating means starts its back stroke, whereby to release the jaws from the tube.

4. A method according to claim 1 in which said expanded portions are die-smoothed without sub Y stantial change in wall thickness 01 the expanded portion.

FRITZ SINGER. 

